Snippets in www-Sharp are very powerfull and easy to use. They not only support raw text but also let you run simple (and not so simple) scripts.
Scripts run on html page that is displayed to user the way similar to window.showModalDialog(). When dialog closes it should return generated string in window.returnValue. The first "|" char shows position of cursor after inserting snippet text (cursor position is set only in www-Sharp syntax editor, on other targets this char will be removed).
When you had wrote snippet page, you should add snippet with type "Command" (right-click on custom snippets tree and choose appropriate item in menu). Caption is text shown in tree, description is shown as hint. Command itself has two parts separated by "|" char. First part is URL (you can register URL with www-Sharp.Runtime or add your page into Snippets folder under directory where www-Sharp is installed, its URL is www-sharp://www-Sharp.Snippets/). Second part is parameters - it is the same parameters as those used by window.showModalDialog().
Of course, you may drag-and-drop snippets onto the new location.